Apparatus for conveying and discharging bulk materials

ABSTRACT

An apparatus and method for conveying and discharging bulk material including a material feed hopper, a screw conveyor, a transition area and a rotary air valve. The feed hopper is divided by a diverter which distributes feed material into the two ends of a trough having a converging screw conveyor. The converging screw conveyor distributes feed material into a transitional holding area for feeding into a rotary air valve. The rotary air valve has a helical vane design and is equipped with at least one cutting knife to control the amount of bulk material distributed in the pockets between the vanes. A blower provides pressurized air flow into and through the rotary air valve. The pressurized air carries the bulk material from the rotary valve through a conduit to discharge the bulk material at a remote distance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a device for conveying and discharging bulkmaterial such as bark mulch or any granular or pulverized material.

2. State of the Art

There are a number of conveying devices suitable for granular orpulverized material which utilize screw conveyors and rotary valves.None, however, are particularly suited for conveying and dischargingbark mulch. Bark mulch is defined as a mixture of organic and/orinorganic materials usually comprised largely of plant and woodresidues, which is generally composted and processed and is used mostlyin the agricultural industry as a soil amendment, a ground cover forerosion and weed control, or for decorative purposes in landscaping. Theknown designs are all subject to jamming due to the build-up of barkmulch which tends to clump together and move as a large mass, instead ofbeing easily shearable and moving as individual particles.

"Bulk Feed Body" is disclosed in Hoffstetter, U.S. Pat. No. 2,939,592,in which a screw conveyor feeds an inlet to a rotary valve. This deviceis primarily designed for grain or dry loose material. The apparatusutilizes a single screw conveyor which would move material such as barkmulch, but would result in compartmental bridging. The consequentbuild-up of the bulk material could rupture the end wall. Wolford, U.S.Pat. No. 3,443,763, also discloses a bulk feed apparatus in which ascrew conveyor feeds an inlet to a rotary dispensing head. Likewise, theWolford apparatus discloses a single screw conveyor used for displacinggrain, salt and other free-flowing material. Similar problems in termsof build-up of material exist with this apparatus when utilized formoving materials such as bark mulch. The Wolford apparatus employs amaterial handling dispensing head and basically slings or throws thefeed material by centrifugal force.

Temple, U.S. Pat. No. 2,757,049, for a "Flour Valve." It uses a helix ina rotation away from the helix angle in order to vent air into the feed.This system is also particularly adapted to freeflowing feed material.

Hickey, et al., U.S. Pat. No. 3,263,592, discloses an "Apparatus forProcessing Fat-Containing Solids" which is not adaptable to dischargingbulk materials. The Hickey machine discloses a single screw conveyorhaving the disadvantages discussed above.

"An Unloading System for Bulk Material Bins," Nadolske, U.S. Pat. No.3,270,921, uses a moving air lock for displacing grains. The Nadolskeapparatus includes a moving air lock with rubber tipped vanes. Theapparatus disclosed in Nadolske would be prone to continuous jamming ifutilized to displace bark mulch, as the long fibrous nature of thematerial tends to fold the airlock seals back and material bridges inthe hoppers.

Burinsky, U.S. Pat. No. 3,314,596, for a "Forage Blower" discloses theuse of an angled knife in conjunction with straight vanes on a fan alongwith a single screw conveyor. The knife is positioned on the outlet sideof the fan. The disadvantages of the single screw conveyor have beendiscussed previously. The Burinsky apparatus would not be capable ofconveying material because this type of fan will not build air pressureif a large portion of material plugs the fan inlet or outlet. This is ahigh speed application as opposed to a low speed heavy torque apparatusas disclosed in the present invention. Furthermore, the fan utilized inthis apparatus is extremely noisy, and when handling bark mulch, a veryhigh strength fan would be required.

Vinyard, U.S. Pat. No. 3,348,652, discloses the use of a convergingscrew conveyor system, but unlike the present invention, it gathersrandomly spaced debris with the conveyor and seldom, if ever, running atfull capacity due to the design of the conveyor housing.

Johnson, U.S. Pat. No. 3,926,377, is an apparatus for moving granulatedand pulverized material. The feed drops through an air lock. Theapparatus is not suited for conveying fibrous materials. Fibrousmaterials tend to jam the airlock and plug the distributor disks.

Boyhont, U.S. Pat. NO. 4,109,966, discloses a pneumatic conveying devicewhich utilizes a single screw press to dewater pulp type material.Stringy material such as bark mulch would plug up the inlet and outletof the chamber of the Boyhont device.

Oury, U.S. Pat. No. 4,117,920, discloses a converging single pitch screwconveyor. The "Auger Hopper" disclosed in Oury has no means to metermaterial other than the size of the outlet opening in the trough.

Machnee, U.S. Pat. No. 4,432,675, for a "Pneumatic Feed Control forPneumatic Seeder and the Like" shows an air seeder which is not suitedfor displacing bark mulch because the shear points would tend to jam up.Small orifices would plug and this type of fan, like that used in theBurinsky devise, would lose air pressure.

Hellerman, U.S. Pat. No. 4,486,126, a "Pneumatic Conveyor for Silage andHaylage" is a variation of the Burinsky patent which discloses rotarycutting knives which counter-rotate to the airlock vanes. The knifesmove the material back into the gravity feed system and act as wipersrather than shear points. Tenacious fibers as in bark mulch would jam,require high power and large vanes to handle induced stresses.

Schumacher, U.S. Pat. No. 4,617,177, shows a screw to dewater rawmaterials and is not at all related to the present application. A Germanpatent, Patent No. 374033, also shows the state of the art of devicesused for conveying materials.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an apparatus forconveying and discharging granular or pulverized material, especiallybark mulch.

Another object of this invention is to provide a novel conveying systemwhich readily accommodates the moisture content and texture of barkmulch without jamming.

Another object of this invention is to provide a method for displacingfeed material which is difficult to handle over long distances.

Still another object of this invention is to provide an apparatus inwhich the feed material meters itself into a rotary air valve.

Yet a further object of this invention is to provide a device fordischarging bulk material which utilizes an air valve with abi-rotational rotor to preclude jamming.

The objects of this invention are achieved by a device which includes afeed hopper assembly having a diverter which displaces feed material tothe ends of the hopper. A converging screw conveyor transports andmeters feed material to an outlet where feed material is dropped orforced into a transition area. From the transition area, feed materialenters the rotary air valve. The rotary air valve is equipped withhelical vanes and cutting knives in order to ensure control of theproper amount of the feed material into a conduit through whichpressurized air flows in order to displace the bulk material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in connection with the annexed drawingswherein:

FIG. 1 is a plan view, partly in section, showing the conveying anddischarging device of the present invention;

FIG. 2 is a side plan view showing the present invention.

FIG. 3 is a plan view of the rotary air valve of the present invention;

FIG. 4 is a side elevational view, partly in section, of the rotary airvalve;

DESCRIPTION OF THE PREFERRED EMBODIMENT

The device of the present invention comprises a hopper assembly (10) ofbasically rectangular cross section in length and square cross sectionin width with an open top and bottom. Placed midway across the length ofthe hopper (10) is a diverter (12) typically wedge-shaped that dividesthe hopper openings into two halves (14). The diverter (12) ispositioned at or near the center of the hopper length. The sides (16) ofthe diverter (12) are usually positioned off parallel and sloping insuch manner that feed material is encouraged towards the end wall (18)of the hopper (10) and downwards to the screw conveyor (22) withoutbridging. The rectangular section forming the hopper front may be hingedat the bottom to allow it to fold down for easy loading access.

Mounted directly onto and generally below the hopper assembly is aflared trough (20) with a concave, semi-circular bottom containing aconverging screw conveyor (22). The longitudinal axes of the trough(20), the screw (22), and the hopper assembly (10) are all parallel. Theconveyor trough (20) is open on the top toward the ends with theopenings being the ends of the hopper (18) and the sloped sides (16) ofthe diverter (12). Under the diverter (12) is a shroud (24) whichtransforms the open trough (20) into a conduit of essentially circularshape.

The screw (22), located concentrically in the concave arc of the trough(20), is supported and rotates on bearings (28) mounted on troughendplates (26) which coincide with the hopper ends (18) and is driven bya motor (31) connected to the screw conveyor shaft (29) by a drive (30).The screw flighting is divided in half or nearly in half across the axisof rotation, with one side being right hand and the other being lefthand. Thus when rotated in the proper direction, material is conveyedtoward the center of the conveyor (22).

The pitch length of the right and left hand screw (22) is the same, andis one half of the outside diameter of the screw flighting. This pitchis uniform until the flighting extends approximately one pitch lengthunderneath the trough shroud (24). At this point, the pitch length ofthe flighting abruptly changes to equal the outside diameter of thescrew. This screw pitch is maintained until the flighting ends at ornear the conveyor midpoint. By varying the pitch along the length of theconveyor (22), the feed material is effectively metered.

Located at the conveyor midpoint is a discharge opening (32) in thebottom of the conveyor trough (20). The opening (32) is approximatelythe same width as the outside diameter of the screw flights and is ofsufficient length so approximately one half of the final pitch length ofboth the right and left hand screws is exposed to the opening.

Located generally beneath the opening (32) is a transition area (34)leading to the material inlet (46) of a rotary air valve (42). Thistransition area (34) is equipped with access doors (36) for inspectionof the air valve/transition area (42/34), and to allow maintenance ofthe rotary air valve (42) without its removal. The doors (36) areequipped with safety interlock devices (38) which will stop the rotaryair valve (42) and the screw conveyor (22) rotation any time either ofthese doors (36) is opened.

The rotary air valve (42) consists of a cylindrical, tubular housing(44) having a section of the cylinder wall of the housing (44) removedto serve as a material inlet (46). The material inlet (46) receivesmetered bulk material from the screw conveyor (22) and is approximatelythe same size as the discharge outlet (32) in the bottom of the conveyortrough (20). In general, the material inlet (46) is oriented so that itis located above the axial center-line of the cylindrical housing (44).Bordering along each of the two longitudinal sides of the material inlet(46), and parallel to the air valve rotor shaft (50), is a mountingshelf (114) containing an adjustable cutting knife (106) ofapproximately the same length as the material inlet (46). The knives(106) are oriented on the shelves (114) so the honed cutting edges(110), in general, oppose each other and face the material inlet (46)opening in the housing (44), extending into said opening (46) so thehoned cutting edge (110) can be adjusted by the screws (112) on theshelf (114) to a minute distance within the inside diameter of thehousing (44). The knives (106) are held in place by clamping bolts (113)threaded into the shelf (114).

Concentric with the axial center-line of the housing (44) is a rotor(40) comprised of a central shaft (50) with multiple vanes (52) forminga multiple of pockets (54), with each vane (52) extending outward fromthe shaft (50) center-line to within close proximity of the insidediameter of the cylindrical housing (44). When viewed from a radialdirection, all vanes (52) are mounted at, but not limited to, a commonangle which may vary between five and ten degrees as compared to theaxial center-line of the shaft (50). The rotor (40) is powered by amotor bi-rotational (57) and drive (56). As the shaft (50) rotates, thevanes (52) move circumferentially below the material inlet (46) area,and in general toward the cutting edge (110) of one cutting knife (106)and away from the other cutting knife (106). As the outside edge of avane (52) passes the cutting edge (110) of the knife (106) it is movingtoward, a cutting force is created on any material trapped between thetwo. The cutting action is enhanced by the close proximity of the honedcutting edge (110) of the knife (106) to the edge of the rotor vanes(52). Furthermore, with the vanes (52) canted at an angle, the cuttingaction occurs gradually as the edge of each vane (52) passes the cuttingedge (110) of the knife (106) in an incremental manner along theirrespective lengths. Having a knife (106) on both sides of the materialinlet (46) allows this cutting action to occur whether the rotor (40) isturning in either a clockwise or counter-clockwise direction.

End plates (60) cover each end of the cylindrical housing (44) andcontain bearings (62) on which the rotor (40) is supported and rotates.Each end plate (60) contains one opening to act as an air inlet (64) oran outlet (66), depending on the direction of air flow. These openings(64, 66) are located on the plates (60) radially between the insidediameter of the rotor vanes (52) and the inside diameter of thecylindrical housing (44). The air inlet (64) and outlet (66) openings,in general, are positioned below the axial center-line of thecylindrical housing (44), and in an offset manner defined by the vane(52) angle. Thus, as the vanes (52) rotate past the air inlet (64) andoutlet (66), they do so in a simultaneous manner, that is, as the edgeof a vane (52) end reaches the side of the air inlet (64) opening, italso reaches the same side of the air outlet (66) opening.

High pressure air is fed by a fan or blower (120) through the air inlet(64). Escape to the atmosphere of the pressurized air through thematerial inlet (46) is minimized by the close proximity of the outsidediameter of the rotor vanes (52) to the inside diameter of thecylindrical housing (44). Thus, the high pressure air is channeledthrough each pocket (54) as the vanes (52) rotate past the air inlet(64) and outlet (66). To diminish air leakage which occurs between theend plates (60) and the ends of the rotor vanes (52), a seal plate (70)of antifriction material is placed at each end of the rotor (40). Theseal plates (70) have roughly the same outside diameter as the insidediameter of the cylindrical housing (44). The seal plates (70) are alsoequipped with openings through the center of sufficient size to allowthe rotor shaft (50) to extend through and openings of roughly the sameshape, size, and location as the air inlet (64) and outlet (66). Theseal plates (70) are held stationary with respect to the end plates (60)and the cylindrical housing (44), with the rotor (40) ends turning incontact with the inside surface of the seal plates (70). As the sealplates (70) wear, shims (72) between the rotor end plates (60) and therotor housing (44) can be removed to bring the seal plates (70) backonto contact with the rotor (40).

Bulk material, such as bark mulch, is fed into the hopper (10) by meansof, but not limited to a loader, a conveyor, or a live bottom or dumptruck. Material either falls directly through the hopper (10) into thescrew conveyor trough (20), or comes in contact with the diverter (12)and is influenced downwards to the trough (20) openings at the ends ofthe screw conveyor (22). As the material fills the trough (20), thescrew (22) acts upon it, moving it from the outside ends of the trough(20) toward the converging point of the conveyor (22). If sufficientmaterial is fed to the trough (20) openings to cover the screwflighting, the screw conveyor (22) will run full. The screw conveyor(22) ends run full until the material reaches the pitch length changeunder the shroud (24). With the increased volume between the flights,the material level drops to less than full on each side. The materialfrom one end is conveyed until it is thrust upon material being conveyedfrom the other end. The reduced capacity of the full pitch convergingscrew flighting (22) and any open area between the converging screwflights allows enough area for the two converging masses to interact andinduce forces upon each other to break one another apart. This isparticularly advantageous when the feed material is fibrous and tends tomove as large mass instead of moving as individual particles such asbark mulch.

The loose material falls, or is forced through the trough dischargeopening (32) by the aforementioned converging action. The material fallsthrough the transition area (34) into the material inlet (46).

As material falls into the rotary air valve (42), the rotating pockets(54) fill with material, usually in a random uneven fashion. Withfibrous materials such as bark mulch, large pieces of materialprotruding out of a pocket (54) have a tendency to get jammed betweenthe rotor housing (44) and the trailing vane (52) of that pocket as thatvane (52) starts to pass from the material inlet (46) into the housing(44). The cutting knives (106) greatly reduce jamming by cutting anyfibrous material extending beyond the outside diameter of the vanes(52), while the angled vane (52) reduces the cutting area so only asmall portion of the knife (106) is cutting at any moment. The angledvane (52) also helps to more evenly distribute the material in thepockets (54) between the vanes (52) by allowing potential overage tospill to the next pocket (54), or axially down the pocket (54). If alarge piece of material does jam the air valve (42), the rotation of theair valve rotor (40) automatically reverses allowing the materialcausing the jam to fall into the pocket (54) or to be cut by the otherknife (106).

Material contained in the area defined by the pockets (54) and thehousing (44) rotates around with the rotor (40) until the vane (52) endscome into communication with the air inlet (64) and outlet (66) ductssimultaneously. High pressure air from a blower (120) is passed into thepocket (54) where the pressurized air picks up the bulk material andconveys it out of the air valve (42) and into a discharge conduit (68)for distribution. The discharge conduit (68) may be fitted with aflexible hose (69) for remote distribution of the bulk material or maybe directly connected to other conveying devices for transfer of bulkmaterials.

This device is suitable for permanent installation. Yet it has the addedadvantage of mobility and may be easily transported from place to placein order to achieve the desired movement of material.

It is intended that the foregoing be merely a description of thepreferred embodiment and that the invention be limited solely by thatwhich is within the scope of the appended claims.

We claim:
 1. An apparatus for conveying and discharging bulk materialcomprisinga hopper feeder assembly having a diverter dividing saidhopper; a trough mounted generally below said hopper assembly; aconverging screw conveyor mounted within said trough; a means fordriving said screw conveyor; an opening in the bottom of said trough; atransition area located beneath said opening; a rotary air valve locatedbeneath said transition area; a means for driving said rotary air valve;said rotary air valve having a material inlet, a central shaft withmultiple vanes mounted at a five to ten degree angle to the axis of saidshaft defining pockets between said vanes; at least one cutting meanspositioned on a mounting shelf along the longitudinal axis of saidmaterial inlet; said rotary air valve having an air inlet and an airoutlet, said outlet offset from said inlet by the angle of said vane sothat air fed through said inlet is channeled through said pocket to saidoutlet; a means for conveying bulk material from said outlet of saidrotary valve; and a means for supplying pressurized air to said airinlet.
 2. An apparatus for conveying and discharging bulk materialcomprisinga hopper feeder assembly having a diverter dividing saidhopper into two halves, said diverter feeding material into said halvesof said hopper; a concave semi-circular trough mounted generally belowand in communication with said halves of said hopper assembly; a shroudextending approximately the length of said diverter centered over saidtrough; a converging screw conveyor having variable pitch mounted withinsaid trough; a means for driving said screw conveyor; an openingcentrally positioned in the bottom of said trough; a transition arealocated beneath said opening in said trough; a rotary air valve locatedbeneath said transition area; a means for driving said rotary air valve;said rotary air valve having a cylindrical housing with a materialinlet, a central shaft with multiple vanes mounted at a five to tendegree angle to the axis of said shaft defining a pocket between twoadjacent vanes; at least one cutting means positioned on a mountingshelf along the longitudinal axis of said material inlet and parallel tothe air valve rotor shaft; said rotary air valve having an air inlet andan air outlet, said outlet offset from said inlet by the angle of saidvane so that air fed through said inlet is channeled through said pocketto said outlet; a means for supplying pressurized air to said air inlet;and a means for conveying bulk material from said outlet of said rotaryvalve.
 3. An apparatus for conveying and discharging bulk materialaccording to claim 1 wherein said material inlet has at least twocutting means, opposing each other positioned on opposing sides of saidmaterial inlet.
 4. An apparatus for conveying and discharging bulkmaterial according to claim 3 wherein said rotary air valve is driven bya bi-rotational motor.
 5. An apparatus for conveying and dischargingbulk material according to claim 2 wherein said material inlet has atleast two cutting means, opposing each other positioned on opposingsides of said material inlet.
 6. An apparatus for conveying anddischarging bulk material according to claim 5 wherein said rotary airvalve is driven by a bi-rotational motor.